A. Field of the Invention
The present invention relates generally to a new and improved spectrometer; and more specifically, to a new and improved spectrometer capable of conducting both turbidimetric and colormetric measurements.
B. Description of the Prior Art
Regular transmission optics are most commonly used for colormetric measurements, while diffuse transmission optics are commonly used for turbidimetric measurements. Due to these different optics, a single spectrometer cannot perform both colormetric and turbidimetric measurements. Moreover, if conventional regular transmission optics are used to perform turbidimetric sample measurements, accuracy problems occur. These accuracy problems manifest themselves in a large instrument to instrument bias due to opto-mechanical variations between instruments. Conventional optics typically eliminate inaccuracy by calibration of each instrument using samples of known turbidity. A correlation between the known levels and the instrument lends results in a calibration curve that is used to correct for bias. Another method of removing the inaccuracy is to precisely align each optical system in the manufacturing process to eliminate the opto-mechanical variations. While both methods of correction are viable, neither is an acceptable procedure when manufacturing a large number of instruments.
Several systems are known in the prior art; however, none of these systems includes a dual beam spectrometer that can perform both turbidimetric and colormetric analysis. For example, U.S. Pat. No. 4,457,893, discloses a system that measures light absorption of a liquid medium with an antibody before and after agglutination reaction by using a wavelength of light which is absorbable by the antibody. This system, however, can perform only colormetric measurements of the agglutination reaction. Another system is disclosed in Japanese Patent 1,112,162. This system includes two photometric systems used to perform both regular and diffuse transmission measurements of agglutinated samples. Again, two systems are necessary. Japanese Patent No. 63/191,962 discloses a system or instrument that automatically performs immunoassays making use of a latex agglutination reaction. U.S. Pat. No. 4,766,083 discloses a system that uses a laser for a light source to detect diffuse transmission. A laser is not necessary in the present invention. U.S. Pat. No. 4,429,040 discloses an assay that is used for detection and determination of fibrin monomer in blood plasma. British Patent No. 1,598,129 discloses a system or an instrument that automatically performs immunoassays using a latex agglutination reaction.
In Soviet Union Patent No. 1186958, there is disclosed a system of calibration for a regular transmission photometer. A patent for an optical sample cell is disclosed in Soviet Union Patent No. 883714. Similarly, a calibration procedure for a regular transmission spectrometer correction filter is described in Soviet Union Patent No. 1153240. U.S. Pat. No. 3,436,187 discloses a method of estimating turbidity employing polystryrene latex suspensions as samples. Also, U.S. Pat. No. 4,495,293 discloses a fluorometric assay of ligands by a reaction with a reagent which alters emission properties of a fluorescer.